preheat oven to 350. put 3 eggs, 1 cup water, and 1/2 cup vegetable oil into mixing bowl and mix until super foamy (mix slow speed at first and then switch to medium)
add in cake mix and mix for ~2 minutes on medium speed
butter or spray oil onto cake pan and pour in cake mix
bake for 28-34 minutes (28 works for me) but watch to see if it bakes too long
take cake out of oven, poke holes with a fork all around the cake
boil water and pour 1 1/2 cups into each measuring cup. mix in red and blue jello, 1 in each cup. stir until dissolved. add 1/4 cup cold water to each cup
pour red jello onto one side of cake (slowly) and blue in the other. put in fridge overnight and top with cool whip. enjoy!